Fixes #441: Added openssl-devel to list of dependencies

docs/installation/netbox.md

@@ -10,9 +10,10 @@ NetBox requires following system dependencies:
 * libffi-dev
 * graphviz
 * libpq-dev
+* libssl-dev
 
 ```
-# sudo apt-get install -y python2.7 python-dev git python-pip libxml2-dev libxslt1-dev libffi-dev graphviz libpq-dev
+# sudo apt-get install -y python2.7 python-dev python-pip libxml2-dev libxslt1-dev libffi-dev graphviz libpq-dev libssl-dev
 ```
 
 You may opt to install NetBox either from a numbered release or by cloning the master branch of its repository on GitHub.